West Nile Virus in Horses: Causes, Symptoms, Prevention & Treatment
The barn-ready guide to WNV—how infection happens, what to watch for, which tests your vet may run, when to vaccinate, how to cut mosquito pressure (hello, Citraquin®), and how to rehab with show-smart comfort.
Life Cycle & How Infection Happens
West Nile virus circulates between mosquitoes and birds. Horses (and humans) are dead-end hosts: they become infected via mosquito bites but do not transmit the virus onward. That means an affected horse isn’t contagious to barnmates; the shared risk is mosquito exposure in your area.
Early Warning Signs & Neurologic Manifestations
- Early clues: low-grade fever, depression, reduced appetite, subtle behavior changes
- Neurologic signs: ataxia/incoordination (often hind-end first), weakness, muscle tremors/fasciculations (face/neck), hyperesthesia, cranial-nerve deficits (difficulty swallowing, impaired vision), and in severe cases recumbency
- Outcomes: prognosis varies with severity and care; some survivors have lingering deficits that improve over weeks to months
Heads-Up Any rapidly developing neurologic sign is an emergency. Call your veterinarian immediately and keep the horse calm and safe while you wait.
Diagnosis & Testing
Serology (Antibody Tests)
IgM capture ELISA indicates a recent immune response. Many labs also offer combined IgM/IgG panels to help distinguish recent infection from prior exposure or vaccination. Your vet will interpret results alongside clinical signs.
Advanced Testing
Depending on signs, your veterinarian may add PCR on select samples (e.g., CSF or nervous tissue in special cases) or repeat serology to confirm trends. Vaccination status and timing matter when interpreting results.
Pro Tip Keep a simple health log—temperatures, appetite, and behavior notes can sharpen the diagnostic picture and track recovery.
Vaccination & Mosquito Control
Vaccination (Core)
- Primary series: typically two doses 4–6 weeks apart for naïve adults
- Booster: annually before mosquito season; in higher-risk regions or classes (young, seniors, extended vector seasons), vets may recommend semi-annual boosters
- Foals & broodmares: follow your veterinarian’s protocol and label guidance
Layered Mosquito Control
- Eliminate standing water; clean stock tanks/buckets regularly
- Bring horses in at dusk/dawn; run fans and use screens where possible
- Groom checks after turnout; manage weeds/brush and rodents
- Apply a repellent: Citraquin® is a natural, citronella-powered option riders use against flies, mosquitoes, and ticks. Get step-by-step application here: Citraquin® How-To Guide.
Treatment & Prognosis
- Supportive care: anti-inflammatories, fluids, attentive nursing, sling support if needed, and quiet housing to prevent injury
- Monitoring: close observation of hydration, temperature, feed intake, and neurologic status—adjust care with your veterinarian
- Prognosis: varies; earlier recognition and strong supportive care improve odds
Safety Follow your vet’s medication directions exactly. Do not improvise with unapproved substances.
Recovery & Rehab (Comfort)
Rehab Basics
- Quiet environment; consistent handling and routine
- Vet-guided return-to-movement: start with short, calm hand-walks if safe
- Balanced farrier schedule; good footing to reduce slips
- Hydration and nutrition dialed to appetite and weight goals
Show-Smart Comfort
Keep conditioning comfortable with sensation-free, under-wrap friendly support:
Non-menthol, non-alcohol, and show-aware—fits year-round routines while you rebuild strength.
West Nile Virus — FAQ
Are horses contagious to each other?
No—horses are dead-end hosts and don’t transmit WNV to other horses or to mosquitoes. The shared threat is mosquito exposure.
When should I vaccinate?
Work with your veterinarian to vaccinate before mosquito season each year. Naïve adults usually need two doses 4–6 weeks apart, then annual (or semi-annual in higher-risk scenarios) boosters.
What tests confirm WNV?
IgM capture ELISA suggests recent infection; IgM/IgG panels, PCR on select samples, and repeat testing help your vet build the full picture.
What’s the typical recovery window?
Some horses improve within ~1–2 weeks; others take longer and may have residual deficits that trend better with time and careful rehab.
Will repellent alone protect my horse?
No single step is perfect. Stack strategies: vaccination, environmental control, stabling during peak mosquito hours, grooming checks, fans/screens, and a repellent like Citraquin® 32oz.
Educational note: This article is for general information and is not a substitute for veterinary diagnosis or treatment. Always consult your veterinarian for individualized care.
